My bike is getting goofy

[c-152]

I have been having trouble with my bike for a little while.  First, it wouldnt stay running during at a race.  It was bogging and stalling a bunch.  Thanks to the help og Hughes and others It reset the mixture screw and it doesnt seem to stall when lugging it.  Now it stalls after I shut of the throttle after a long run at anything over 3/4 throttle.  This useually happens as I am going into a turn.  It then fires right back up on goes fine.  until I go down another straight stretch.  It almost seems like it is running to lean.  I have read a lost of the jetting posts to try and figure it out and have some great info that I am going to mess with however I can help but think it might be the power valve.  It all started to run poorly after I changed the clutch a couple of weeks ago.  I took the side cover off and rechecked the gear and everything looks fine.  Does anyone know how to make sure the exhaust valve is functioning properly.  I know I can check the actuating arm with the little plastic cover off but I do not know anything else.  Let me know your thoughts as I am open for suggestion

Thanks

[hughes]

Did or have ever checked the float height? Question for you. If you was to run 3/4 throttle of more and then shut the throttle back to idle does the engine die (not hitting the brakes but letting the bike coast after shutting the throttle down)? I have a bad habit of stalling my bike going into turn to fast and locking up the rear wheel with out any clutch or throttle. Give us the details of what you do when you are coming into a turn.

[c-152]

The bike sometimes dies as soon as I pull in the clutch as I am entering the corner even if I am pumping the throttle - like it is out of fuel.  I am going to check the float hieght tonight.  I know what you mean about no clutching and locking the rear wheel up then the bike stalls but this is different.  In fact last sunday I got into the habit of coasting through the corner then clutching and reving the bike out.  It seemed to keep the bike running almost as thought it was running out of fuel from the long run and then the coasting allowed time for the carb to build up more fuel then it would run again.  If I clutched before the turn, it would stall every time after it warmed up.  I would think if the float was set to low then it would also stall during the long run but it doesnt. I am going home to tinker with it tonight and plan on testing it out again this sunday.

[hughes]

Sure sounds like some fuel related issue with carb. Keep us informed.

[c-152]

Thanks - I will let you know what I find

[Friar-Tuck]

 I was wondering ,  is the bike getting hard to start? 
chipped ,cracked worn reeds? (loss of signal strength)

        If adjusting the air screw richer helped, could the tank vent or carb vents be restricted ?, allowing larger throttle openings enough vacuum to draw fuel and when throttle is chopped the sudden loss of signal strength shuts you down.
   Not discounting the previous float level suggestions, as the symptoms would be just like a partially clogged fuel filter in a car. You could only run as fast as the fuel pump could keep the bowl full.  Pulling in the clutch and trying to keep the old girl running may not provide the same "draw" as "coasting" pulling more fuel in to the carb.
   There is a small filter on the inside of the tank attached to the fuel fitting that may
 be giving you a problem as well as the small passages in the petcock itself.
   Oy, I'm not very good 'Splain-en stuff  but maybe some of this might help find the buggar.
 Tuck \o/

[c-152]

Frair-Tuck
I checked the reeds before I left this Sunday.  I also double checked all of my jetting settings and they were all stock except for the clip was set to full lean so I moved it down one thinking that would help.  I didn't know about the little fuel filter in the petcock and will check that - thanks.  The bike still starts first kick without a problem. I also checked the tank and carb vents and they looked okay.  Thanks for the info.

As for Sundays ride this is what happened.  I rode around for about 20 minutes on some tight trails and everything was okay until I came to a short steep hill and had to open it up to make the hill.  The bike sputtered all the way up and I lopped out at the top however it did not stall.  I tried this several times with the same result.  I then reset the carburetor to full lean and it slightly bogged but had plenty of power for the hill and didn?t stall.  It definitely pulled better with the leaner setting. 

I think for the bike to run perfect, I need to get to a leaner main jet however I am always scared of leaning a bike out to much. 

I guess the thing that I can get over is if it isn?t the exhaust valve, which seems to be operating fine, then the only variable for running bad all of the sudden has to be the change in temperature.  I had been riding in 70 degree weather and now its 80s - 90s and muggy.  Now it is very possible that I have this all screwed up but I always thougth as the temp went up, the bike would need to be set up a littler richer.

Thanks for the advice guys, I am seeing progress as well as learning a lot about tuning a bike.  I have always been comfortable working on bikes but tuning them has always been tough

[Hillclimb#42]

 I'm not sure about a complete cure, but I am sure that when the temps warm up, it runs more rich. Check the plug. Should be brown. If you're black you need to lean it out some. A lean condition will have alot of run-on after you close the slide and the idle will be fast and it will have a new ping to it when pinned. Gearing may also bog the motor on steep hills. The tip from Hughes about float adjustment could be something too. Check the jetting chart for temps, elevations and mixture settings.
 Tuning according to stock specs is accurate as long as you have a fresh motor and run pump gas. Racing fuels and worn rings usually need to be fattened up to tune.
  After jetting my bikes to stock, I usually will check plug color, if I suspect I need to adjust mixture screw. 

[don46]

Frair-Tuck
I checked the reeds before I left this Sunday.  I also double checked all of my jetting settings and they were all stock except for the clip was set to full lean so I moved it down one thinking that would help.  I didn't know about the little fuel filter in the petcock and will check that - thanks.  The bike still starts first kick without a problem. I also checked the tank and carb vents and they looked okay.  Thanks for the info.

As for Sundays ride this is what happened.  I rode around for about 20 minutes on some tight trails and everything was okay until I came to a short steep hill and had to open it up to make the hill.  The bike sputtered all the way up and I lopped out at the top however it did not stall.  I tried this several times with the same result.  I then reset the carburetor to full lean and it slightly bogged but had plenty of power for the hill and didn?t stall.  It definitely pulled better with the leaner setting. 

I think for the bike to run perfect, I need to get to a leaner main jet however I am always scared of leaning a bike out to much. 

I guess the thing that I can get over is if it isn?t the exhaust valve, which seems to be operating fine, then the only variable for running bad all of the sudden has to be the change in temperature.  I had been riding in 70 degree weather and now its 80s - 90s and muggy.  Now it is very possible that I have this all screwed up but I always thougth as the temp went up, the bike would need to be set up a littler richer.

Thanks for the advice guys, I am seeing progress as well as learning a lot about tuning a bike.  I have always been comfortable working on bikes but tuning them has always been tough

When the temperatures warm up you will need to lean your jetting, In the back of your owners manual there is a conversion chart for temp and elevation, I don't use it, but, it does explain how to jet. I'm more of a seat of the pants jetter, I know what rich is and I jet down till it doesn't feel rich anymore. Based on your description I would say your rich.

[hughes]

Don is right about the temps. Check the float height before you change jetting.

[2000desertkx500]

I just had a buddy go through something like this on his KTM. After hours of frustration and pulling hair out 2 carb rebuilds, it ended up being the fuel petcockon the tank. Was clogged. Not lettig enough fuel into the carb.

[c-152]

Thanks for all the good info guys.  I had a 168 main and switched to a 162.  I am going riding tonight so I will post my findings. If it doesn?t work then I am going to look at fuel flow even though it seems okay.  I am kind of glad this is happening now because I do not plan on racing until august so I have a while to get it correct and I need to learn a little more about carburetion anyway.  Thanks